In general, a photographic silver halide light-sensitive material (hereinafter sometimes referred to merely as a "light-sensitive material"), when exposed imagewise and then developed, provides an image or image pattern. In some cases, an antifoggant, a development inhibitor, etc., are added in combination with a development agent to a processing solution for the purpose of improving image quality, and a development accelerator, a sensitizer, etc., are added for the purpose of increasing sensitivity. These additives are called herein "photographically useful compounds".
When such photographically useful compounds are incorporated in a light-sensitive material or film, they seriously reduce sensitivity during the storage of the film, increasing the formation of fog, because they coexist with silver halide. This problem could be overcome if they are controlled to exhibit their activity just at the stage of development. It has, therefore, been considered to use their precursors which are prevented from reacting with silver halide during the storage of the film or at the stage of exposure, but which are decomposable with alkalis so as to release a photographically useful group timely at the stage of development. One of the features of such precursors is that they are prevented from reacting prior to the processing, and another feature is that the timing of releasing a necessary compound at the stage of development can be controlled.
In general, an alkaline solution is used as a developing solution. Therefore, it has been attempted to meet both the requirements, i.e., the proper releasing speed of the photographically useful group at the stage of development and the stability of the raw film during the storage thereof, by utilizing the difference in hydroxy ion concentration between during the storage of the raw film and at the stage of development. However, since the difference in hydroxy ion concentration is not so large for commonly used developers (pH: 8-13), it is difficult to meet both the requirements particularly when the photographically useful group is desired to be released just after the start of development as in the case of a sensitizer, for example.
Various compounds have been developed to solve the above-described problem, including those compounds as described in U.S. Pat. Nos. 4,209,580, 3,241,967 and 4,310,612. These compounds, however, are not satisfactory and must be further improved. They exhibit the necessary photographic performance to a certain extent when used in a light-sensitive material which is to be processed with a processing solution having a pH as high as 13 or more. Even in this case, the storage stability can be ensured only by sacrificing the releasing speed of the photographically useful group at the stage of development.